The invention relates to a multicoordinate measuring machine with two guiding devices, which are arranged parallel to each other and at a distance from each other, between which a cross arm, inserted at right angles, is movable on carriages at either end. The cross arm, in turn has a further carriage, which is movable along its longitudinal axis and carries a measuring head with at least one measuring probe, the actual position of which is detected by an electrical system and indicated by means of an electric output signal.
German Auslegeschrift Pat. No. 2,248,194 discloses a multicoordinate measuring machine, especially for length measurements, and for determining the position and magnitude of openings, contours, projections, etc. This known measuring machine is constructed in the style of a measuring bridge machine and moves with the two parallel columns in appropriate guiding systems. The measuring head itself is mounted on a beam, which is movable on the bridge. The problem with such multicoordinate measuring machines is that the two columns, even if precision is very high, assume different positions during their movement in the allocated guiding systems.
This problem cannot be eliminated completely, even if expensive and technically costly precision elements are used. In order, nevertheless, to determine the exact position of the measuring head in the direction of motion X of the columns, this known multicoordinate measuring machine has two measuring devices, which are installed in each case along the guiding systems of the columns. A third measuring device determines the position of the measuring head along its guiding system on the bridge. These three measuring heads are connected to an electrical system for determining the actual position of the measuring head.
Even though the actual position of the measuring head on the X axis can be determined by this multicoordinate measuring machine with the help of the measuring devices and the allocated electrical system, the technical effort involved, with a total of three measuring devices, does however represent a considerable disadvantage. The fact that more parts are required in order to measure the respective reference position and that several measuring devices are used to determine an actual position of the measuring head, represents a new and additional source of error.